The present invention is used for limiting electromagnetic interference (EMI) in electrical components as they are employed in electrical circuitry. One challenge for designing an electrical circuit is the reduction of electromagnetic interference (EMI) during operation of the circuit. One approach for effecting EMI reduction has been to design circuits in manners to confine components that are sources of EMI to restricted areas. Such an approach is marginally effective and contributes significantly to the time and talent required for circuit layout design. Increased time and talent in design contributes to the cost of circuit layout design, both in dollars and in time required. Many such early designs also proved difficult to manufacture on a production scale with acceptable manifested operating parameters.
Some of the earlier layout techniques included laying specified circuit traces atop one another in an effort to arrange for interlayer electromagnetic interference to cancel out. Another approach has been to place a ferrous bead on a wire connector (such as, for example a jumper wire), or on at least one lead of an electrical component (such as a transistor). Such ferrous beads provided a one-turn inductor. In using a ferrous bead, for example, in connection with a field effect transistor (FET), a bead may be installed on the source lead, on the drain lead, or on both the source lead and the drain lead. Such an addition of a one-turn inductor to the leads affects rise time or other operating characteristics of the FET in a manner that ameliorates the effects of high frequency noise on the FET. High frequency noise is a significant source of EMI. It is a characteristic of Fast Fourier Transform circuitry that a transform having a square shape involves a significant amount of high frequency noise. If the Fast Fourier Transform has the shape of a trapezoid (which would occur, for example, if rise times are affected), there are significantly fewer high frequency harmonics. Fewer high frequency harmonics means less EMI.
Ferrous beads employed on component leads also affect noise spikes. Ferrous beads installed encircling component leads absorb energy at high frequency and, therefore, suppress noise spikes.
The electrical benefits of ferrous beads in ameliorating effects of high frequency harmonics and noise spikes are evident and desirable. There is, however, a physical aspect of installation of the ferrous beads that has so far proven to be detrimental. The beads must be physically affixed in one place. If a bead is able to xe2x80x9crattle aroundxe2x80x9d on a component lead, or a jumper wire or another bead-bearing structure, it will eventually increase the tendency of the bead-bearing structure to break. Indeed, vibration tests in which ferrous beads have become loose from their physically affixing restraint have yielded significant broken parts. One solution in the prior art has been to hot glue or otherwise adhesively affix a bead in place. Vibration tests yielded broken adhesive joints and subsequent broken bead-bearing structures.
There is a need for an apparatus for facilitating employment of ferrous beads to realize their electrical advantages without suffering the physical damage to a circuit in vibratory conditions.
An apparatus for affixing an inductive element in association with a rod within an electrical circuit is disclosed. The rod has a diametral dimension. In its preferred embodiment, the rod is a shaped rod with four or more sides. The inductive element has a generally toroidal shape with an inductive element inner dimension. The apparatus comprises a support member that is flexible to a plurality of orientations including an installing orientation and an installed orientation. The support member is substantially tubular with a first end, a second end and an inner wall defining a support member inner dimension and an outer wall defining a support member outer dimension. The support member inner dimension is substantially equal to the diametral dimension. The support member flexes to the installation orientation when installing the inductive element. The installation orientation establishes the support member outer dimension at less than the inductive element inner dimension appropriately to allow sliding installation of the inductive element about the support element and the rod to an installed position. The installed position is achieved when the inductive element surrounds the support member and the rod with the inductive element situated intermediate the first end and the second end with the support member flexed to the installed orientation. The installed orientation establishes the support member outer dimension at greater than the inductive element inner dimension intermediate the inductive element and at least at one end of the first end and the second end. A method for installing an inductive toroidal element upon a rod in an electrical device is also disclosed. The rod has a first longitudinal axis and a diametral dimension. The toroidal element presents an aperture having an inner toroid dimension. The method comprises the steps of: (a) providing a flexible insulative support member; the support member having a second longitudinal axis extending from a first end to a second end, an inner support dimension generally equal to the diametral dimension and an outer support dimension generally equal to the inner toroid dimension; (b) flexing the support element to situate the support element within the aperture with the toroidal element intermediate the first end and the second end to establish an assembly; (c) situating the assembly upon the rod with the first longitudinal axis generally aligned with the second longitudinal axis; and (d) slidingly positioning the assembly with respect to the rod to achieve an operational locus.
Prior art mounting of inductive elements, such as ferrous beads, on rods, such as component leads or jumper wires, in electrical circuits have not successfully affixed the beads in place. Normal vibration and other forces work the inductive elements loose during normal operation of the electrical circuits. As a consequence, broken leads, cracked beads and related problems have been experienced.
A further advantage of the present invention in each of its embodiments is that the support member absorbs shock forces that may be experienced by an inductor assembly according to the present invention, thereby reducing effects of forces upon the rod as well as upon the inductor member and reducing the risk of fracture or breaking of the rod, inductor member or joints associated with including the rod within an electrical circuit.
It is, therefore, an object of the present invention to provide an apparatus and method for affixing an inductive element with a rod in an electrical circuit that withstands dislodgment and shock forces during operation of the circuit.
Further objects and features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.